A kind of Wavelet transform type low-insertion-loss acoustic surface wave delay line type acceleration transducer
Technical field
The present invention relates to a kind of Wavelet transform type low-insertion-loss acoustic surface wave delay line type acceleration transducer, belong to the acceleration transducer technical field.
Background technology
Acceleration transducer is to utilize the inertial property of object to come one type of inertial sensor of Measuring Object motion conditions.Its output is proportional or the signal of certain relation arranged with the acceleration of motion of motion carrier.The kind of acceleration transducer is a lot, develops also very soon, and that uses comparative maturity at present has piezoresistance type acceleration sensor and a capacitance acceleration transducer.Piezoresistance type acceleration sensor is that to utilize the piezoresistive effect of silicon materials responsive to measuring acceleration, and its gordian technique is to manage will be converted into by measuring acceleration through certain mechanical hook-up the variation of silicon material resistivity.Piezoresistance type acceleration sensor has advantages such as frequency response characteristic is good, measuring method is prone to row, the linearity is good, and its shortcoming is that temperature effect is serious, sensitivity is low.Capacitance acceleration transducer carries out acceleration analysis with converted to changes in capacitance by measuring acceleration.Its essential characteristic is a stable work in work, and temperature drift is little.Yet; Capacitance acceleration transducer will be in the time will being converted into corresponding condenser capacitance variable quantity by measuring acceleration, and acceleration inertial force causes the susceptibility of capacitor plate displacement and speed always is slower than and less than the susceptibility and the speed of support beam upper stresses such as semi-girder variation.
The surface acoustic wave acceleration transducer is to by the susceptibility of measuring acceleration with response speed will be higher than and faster than the acceleration transducer of other types such as condenser type, directly output frequency signal.Simultaneously; The surface acoustic wave acceleration transducer has simple in structure, easy to make; Many advantages such as shock-resistant, stable and reliable for performance, sensitivity height, it is the strong rival of existing acceleration transducer, is a kind of acceleration transducer with bright application prospect.
Summary of the invention
The objective of the invention is to solve the problem of the irregular neighbourhood noise of part to the precision influence of surface acoustic wave acceleration transducer measurement result; Provide a kind of antinoise interference performance strong; Loss is low, is adapted to the acceleration transducer of the application demand of inertia identification in the portable mobile apparatus.
In order to achieve the above object; The invention provides a kind of low-insertion-loss acoustic surface wave delay line type acceleration transducer, it is characterized in that, comprise substrate with wavelet transformation function; The left end of substrate is fixed; Right-hand member load mass piece, the upper surface of substrate are provided with the first input transducer, first output transducer from left to right successively, and the first input transducer is connected with first feedback amplifier respectively with first output transducer; The lower surface of substrate is provided with the second input transducer, second output transducer from left to right successively, and the second input transducer is connected with second feedback amplifier respectively with second output transducer; Described first feedback amplifier, second feedback amplifier are connected with frequency mixer respectively; Described frequency mixer is connected with low-pass filter.
Described substrate adopts piezoelectric to make and forms.
Preferably, described substrate is the quartz crystal cantilever beam structure.
Described substrate upper and lower surfaces is provided with the single phase single direction structure SAW delay line with wavelet transformation function.
The described first input transducer, the second input transducer, first output transducer and second output transducer all adopt the single phase unidirectional transducer structure.
Described mass is the square mass.
The described first input transducer and the second input transducer are the input interdigital transducer; Described first output transducer and second output transducer are output interdigital transducer.
Preferably, described input interdigital transducer is the Wavelet transform type transducer; Described input interdigital transducer sliver envelope is confirmed according to the envelope of Morlet dyadic wavelet function.
The described first input transducer and the second input transducer adopt cuts the toe weighting; Described first output transducer and second output transducer for not weighting etc. refer to length and width band transducer.
Core component of the present invention is the fixing quartz crystal semi-girder of an end; Its free end is the square mass loading of Y through a length of side; The single phase single direction structure SAW delay line that the semi-girder upper and lower surfaces utilizes semiconductor planar technology to process to have the wavelet transformation function; Two lag lines constitute single-mode oscillator with amplifier respectively, form difference structure through the frequency mixer mixing then, help reducing the influence of temperature and transverse acceleration.The output frequency response of the SAW delay line among the present invention is the frequency response of Morlet dyadic wavelet function; This SAW delay line frequency response has the filter function of eliminating noise; Therefore the antinoise interference performance of this SAW delay line type acceleration transducer is strong; And it is low to insert loss, is adapted to the application demand of inertia identification in the portable mobile apparatus.Therefore, the present invention has strong, the low insertion loss of antijamming capability, is adapted to the characteristics of inertia recognition application demand in the portable mobile apparatus.
Description of drawings
Fig. 1 is a kind of structural representation of Wavelet transform type low-insertion-loss acoustic surface wave delay line type acceleration transducer.
Fig. 2 is the vertical view of the quartz crystal cantilever beam structure that an end is fixed in the present embodiment.
Among the figure:
1, substrate; 6, second feedback amplifier;
2, the first input transducer; 7, second output transducer;
3, first feedback amplifier; 8, mass;
4, first output transducer; 9, frequency mixer;
5, the second input transducer; 10, low-pass filter.
Embodiment
Below in conjunction with specific embodiment, further set forth the present invention.
Embodiment
As shown in Figure 1, be a kind of Wavelet transform type low-insertion-loss acoustic surface wave delay line type acceleration transducer, form by two input transducers, two output transducers, two feedback amplifiers, substrate 1, mass 8, frequency mixer 9 and low-pass filters 10.The quartzy semi-girder that substrate 1 adopts the higher piezoelectric quartz of temperature coefficient to process; Substrate 1 surface is provided with the single phase single direction structure SAW delay line with wavelet transformation function; SAW delay line adopts single phase unidirectional transducer-single phase unidirectional transducer structure (SPUDT-SPUDT structure), comprises input transducer and output transducer.The weighting scheme that two transducers of SAW delay line adopt does, the input transducer adopts cuts the toe weighting, and output transducer refers to length and width band transducer for the grade of not weighting.The left end of substrate 1 is fixed; Right-hand member load mass piece 8; The upper surface of substrate 1 is provided with the first input transducer 2, first output transducer 4 from left to right successively; The first input transducer 2 is connected with first feedback amplifier 3 respectively with first output transducer 4, and the lower surface of substrate 1 is provided with successively from left to right and second imports transducer 5, second output transducer 7, the second is imported transducers 5 and is connected with second feedback amplifier 6 respectively with second output transducer 7; First feedback amplifier 3, second feedback amplifier 6 are connected with frequency mixer 9 respectively; Frequency mixer 9 is connected with low-pass filter 10.
The oscillator that the first input transducer 2 of substrate 1 upper surface, first output transducer 4 and first feedback amplifier 3 constitute, responsive to outside acceleration signal; The oscillator that the second input transducer 5 of substrate 1 lower surface, second output transducer 7 and second feedback amplifier 6 constitute; Responsive to outside acceleration signal; But the oscillator of lower surface for reference only; Two SAW delay lines form difference structure, help reducing temperature and ambient noise interference.Two SAW delay line structures are identical, and output terminal links to each other and through frequency mixer 9 mixing, can the variation of external acceleration be converted into the variation output of frequency.
The free end of substrate 1 is that the mass 8 of the square of Y loads through a length of side; The single phase single direction structure SAW delay line that the semi-girder upper and lower surfaces utilizes semiconductor planar technology to process to have the wavelet transformation function; Two lag lines constitute single-mode oscillators with first feedback amplifier 3, second feedback amplifier 6 respectively; Form difference structure through frequency mixer 9 mixing then, help reducing the influence of temperature and transverse acceleration, then through the output of low-pass filter 10 filter away high frequency noise signals.
Substrate 1 is the SAW delay line structure, and the first input transducer 2 is imported transducer 5 with second, i.e. left side interdigital transducer is for wavelet function is cut the toe weighting; First output transducer 4 and second output transducer 7, i.e. the right interdigital transducer is for the grade of not weighting refers to length and width band transducer.The centre frequency of SAW delay line is 68MHz among Fig. 2, so the centre frequency of SAW delay line oscillator is 68MHz.Have the relative bandwidth little (arrowband) of the lag line of filter function, and be low Insertion Loss device.As long as certain phase condition is satisfied in the loss that Amplifier Gain can equalized delay line again, oscillator just can starting of oscillation.
Fig. 2 is the vertical view of the fixing quartz crystal cantilever beam structure of an end.This semi-girder is an isosceles triangular structure, and the material of substrate 1 adopts quartzy.What show among Fig. 2 only is the upper surface of quartzy semi-girder, and the lower surface configuration and the upper surface of quartzy semi-girder are identical.
The present invention has highly sensitive and the good advantage of the linearity; The output frequency response of the SAW delay line in this invention is the frequency response of Morlet dyadic wavelet function simultaneously; This SAW delay line frequency response has the filter function of eliminating noise; Therefore the antinoise interference performance of this SAW delay line type acceleration transducer is strong, and the insertion loss is low, is adapted to the application demand of inertia identification in the portable mobile apparatus.